In certain types of X-ray imaging equipment, such as Kirkpatrick-Baez devices, a number of slightly curved surfaces or plates, typically float glass, are used to focus X-ray radiation incident at low grazing angles, e.g. one or two degrees or less. (Kirkpatrick, P., and A. V. Baez, "Formation of Optical Images by X-rays", Journal of the Optical Society of America, Vol. 38, p. 766 (1948)). Such devices are useful as telescopes for X-ray astronomy and in microscopes for viewing plasma emission.
In one application, the plates are curved or bent by applying forces along only the side edges of the plate so that the front and rear edges are clear for passing X-rays. One shortcoming of such an approach is that the plates tend to form a saddle shape because the center area remains relatively flat compared to the edges where the force is applied. Another bending method that has been suggested uses a torsion bar at each of the front and rear ends of the plate. (Underwood, J. H., "Generation of a Parallel X-ray Beam and Its Use for Testing Collimators," Aerospace Corporation Report No. ATR-76(7493)-4.) The bars are rotated to cause the plate to bend. However, to provide the necessary torsional rigidity to insure uniform bending of the plate, the bars appear to require a thickness of two to three times the thickness of the plate and so seriously diminish the volume available for additional plates in applications where space is limited. It has been proposed simply to heat and reform glass plates to provide the necessary curvature, but it has been determined that upon heating the glass develops warps and wrinkles of its own which are often larger than the required curvature.